The horse’s digestive system may seem quite “delicate”, but what is it that makes them prone to issues like colic, laminitis, and gastric ulcers? The answer to this question can be found the anatomy of their digestive system as well as how it functions.
Horses evolved to move and graze, eating small meals for about 16 hours each day. They are non-ruminant, simple-stomached herbivores and hindgut fermenters, meaning fiber is mostly fermented in the large intestine. This makes them different from ruminants such as cattle, goats, and sheep which are foregut fermenters with a rumen and multi-compartment stomach.
The Equine Foregut
The equine foregut is relatively small when compared to their hindgut. It consists of the mouth, esophagus, stomach, and small intestine. The mouth is, of course, where digestion begins as the horse chews food to reduce the particle size. Horses produce 9-10 gallons of saliva per day as they chew their food which lubricates food particles and creates a bolus—a round mass of food that is easier to swallow. Saliva also helps to buffer acid produced in the stomach.
After leaving the mouth, food travels through the pharynx, into the esophagus, and continues onto the stomach, which can hold about 3-5 gallons.
In the stomach, chemical digestion continues, thanks to the acid continually produced there. However, if horses go for long periods of time without forage, this acid can eat away at the stomach lining, causing ulcers.
From the stomach, food travels into the small intestine where enzymes further digest carbohydrates, proteins, and fats. Since horses don’t have a gallbladder, the liver secretes bile to aid with fat digestion.
Large grain meals may pass through the entire foregut without being properly digested, causing a disruption of the microbes living in the hindgut. This can lead to gas, colic, and laminitis.
The Horse’s Hindgut
The horse’s hindgut is much larger than the foregut, consisting of the cecum, large colon, small colon, and rectum. The hindgut is where structural carbohydrates from forage are fermented by microbes. Volatile fatty acids (VFAs) are produced as a byproduct of this process, providing energy for the horse.
The microbial population in the hindgut is very sensitive and any sudden change in feed, grass, or hay can lead to changes in the pH and cause problems like colic or laminitis. This is why all diet changes should be made slowly, over a period of 7-10 days.
After leaving the small intestine, food, now called digesta, enters the cecum, a large mixing vat that can hold 7-10 gallons and slows the passage of digesta, allowing microbes up to seven hours to digest fiber.
After leaving the cecum, digesta enters the large colon which can hold about 20 gallons. Microbial fermentation continues, producing VFAs, methane, ammonia, B-vitamins, and amino acids. Minerals such as sodium, chloride, and potassium are also absorbed in the large colon. Digesta may take 2-3 days to pass through the large colon but it finally moves to the small colon where water is absorbed and fecal balls of waste products are formed to move toward the rectum.
Products to Support Your Horse’s Digestive System
Though horses are prone to digestive upset, the good news is that there are a number of products designed to protect and support this delicate system. For example, Pro-Guard Probiotics contains beneficial microbes to support digestion and is especially important to feed after a horse has been on antibiotics.
Slippery Elm soothes inflammation of the stomach and intestinal tract and is especially helpful when ulcers are suspected or diagnosed.
Bentonite Clay has detoxifying properties and is helpful for horses with diarrhea, fecal water syndrome, or loose stool.
And finally, Gastrox helps to heal stomach ulcers naturally and without the side effects of pharmaceutical medications.